Interturbine ducts (ITD) are used for channelling hot combustion gases between adjacent turbine stages. ITDs include a generally conical inner wall and a generally conical outer wall between which the hot combustion gases flow. The outer wall is adjacent to the interior of a turbine casing in which the ITD is provided.
Because of thermal expansion, the upstream end of the ITD is generally not attached directly to the turbine casing. The outer wall of the ITD may have an outwardly extending flange with a free end that is very close to the interior of the turbine casing. The expansion caused by intense heat and pressure during operation of the engine generally seals the space between the ITD and the interior of the turbine casing so as to prevent a combustion gas ingestion.
While the above-described arrangement has proved to be satisfactory for most applications, engines with relatively cooler combustion gases and which generate less pressure inside the ITD may require another approach. Overall, it was thus a need to provide an improved seal system for an interturbine duct within a gas turbine engine.